Diagnostic Aids

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

Check the LR turn lamp bulb. If the bulb is open, DTC B3950 will be set.
If the DTC is a history DTC, the fault may be interment. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
An interment short to ground or an open in the following locations may cause an intermittent malfunction to occur:
- The BCM
- The left rear turn signal lamp supply voltage circuit

DTC B3950

Step	Action	Yes	No
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn ON the ignition, with the engine OFF. Place the turn signal switch in the TURN LEFT position. Do the rear turn signal lamps flash on and off?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn OFF the ignition. Disconnect the LH tail lamp assembly. Connect a test lamp between battery positive voltage and the LR turn signal lamp supply voltage circuit at the body control module (BCM) harness connector C2. Does the test lamp illuminate?	Go to Step 6	Go to Step 4
4	Disconnect the BCM harness connector C2. Test for continuity in the LR turn signal lamp supply voltage circuit between the BCM harness connector C2 and the LH tail lamp assembly. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 8	Go to Step 5
5	Inspect for a high resistance or an open at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 8	Go to Step 7
6	Repair a short to ground in the LR turn signal lamp supply voltage circuit. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 8	-
7	Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the replacement?	Go to Step 8	-
8	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC. Does the DTC reset?	Go to Step 2	System OK